Of course third party publishers are the reason if a console will fail or succeed. It's been proven time and time again and dates all the way back to Sega's emergence in the industry.
Now not going to get into an argument, the fact of the matter is, Nintendo forced companies that developed games on their consoles to remain exclusive to them if they wanted to continue development. This is the reason Sega had so many first party titles and third party titles that weren't on Nintendo consoles. Sega actually did really well for having none of the really big third parties that Nintendo controlled, but they still had problems because the lack of a lack of third party support.
Sega CD and the 32X were add ons that got no third party support and failed.
The Nintendo 64 got limited third party support and was a major hit to Nintendo, while Sony got massive third party support and sales blew up immediately. Sega Saturn got third party support but not as much in comparison to Sony.
The Gamecube and Xbox got less third party support than the PS2. Despite the console being less powerful and didn't have any sort of gimmick in control like the Wii, the third party support kept Sony dominating against the competition.
The PSPs lack of third party support because of piracy had it struggling to get sales. It still happened to sell fairly well because the mobile games weren't as big as they are now. Oh and Japan.
Vita and Wii U are selling poorly because they're getting almost no third party support in comparison to the competition. The Vita isn't getting first party support either. Sony expects it to sell without any games.







